1. Field of the Invention
The present invention relates to leak detectors and, more particularly, to portable leak detectors for detecting halogen gas.
2. Background Art
Prior art gas detectors generally, and halogen gas detectors specifically, are well-known in the art for detecting the presence of halogen gas in the atmosphere. Such gas detectors are commonly used to detect for leaks in refrigerant systems that are utilized to cool a living space, an interior of a vehicle, such as an automobile, an interior of a chamber, such as a refrigerator or freezer used for the cold storage of foods, and/or an environmental chamber utilized to expose test pieces or samples to low temperatures.
A problem with such prior art leak detectors is that they often require calibration to detect for the presence of halogen gas surrounding the refrigerant system. Since the concentration of halogen gas in the atmosphere may not be known, such calibration could increase the time to detect for the presence and location of a halogen gas leak thereby increasing the loss of halogen gas from the refrigerant system. In addition, these prior art gas detectors require an operator to utilize two hands to operate thereby making it difficult for the operator to maneuver the gas detector into a position to detect for the presence of a halogen gas leak. Furthermore, such prior art gas detectors typically required a long warm-up interval before accurate readings could be obtained. Still further, these prior art halogen gas sensors included no provision for controlling the power dissipated by its gas sensing element thereby reducing the effective life of the gas sensing element.
It is, therefore, an object of the present invention to overcome the above problems and others by providing a leak detector which can be manipulated with one hand, which enables changes in the concentration of halogen gas to be detected without operator intervention, which provides an auditory and/or visual indication of the change in concentration of halogen gas and which provides circuitry for controlling the power dissipated by the gas sensor of the leak detector in response to a resistance of a heating element of the gas detector changing with use. Still other objects of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.
Accordingly, we have invented a portable leak detector that includes a housing having an inlet in fluid communication between an interior and an exterior of the housing and an outlet in fluid communication between the interior and the exterior of the housing. A gas sensor having a property that changes in response to exposure of the gas sensor to one or more gases is disposed in fluid communication with the interior of the housing. The leak detector can include a probe lamp, a plurality of first indicator lamps supported by the housing and a speaker supported by the housing. A controller supported by the housing is connected to detect the property of the gas sensor. As a function of the detected property of the gas sensor, the controller causes the probe lamp to flash at a first frequency, causes a first group of the plurality of first indicator lamps to illuminate, and causes the loudspeaker to chirp at a second frequency.
The first and second frequencies are preferably the same. Moreover, causing the loudspeaker to chirp at the second frequency preferably includes selectively gating an audio frequency to the loudspeaker at the second frequency.
The leak detector can include a flexible tube and a sensor casing. The flexible tube has a proximal end connected to the inlet of the housing and a distal end. The sensor casing has a proximal end connected to the distal end of the tube, a distal end, and a fluid conduit extending therebetween. The sensor casing can be configured to receive the gas sensor in the fluid conduit and can be configured to support the probe lamp. The gas sensor and the probe lamp can be electrically connected to the controller via electrical conductors preferably received in an interior of the tube.
The leak detector can also include a plurality of second indicator lamps supported by the housing. The controller can cause a select group of the plurality of second indicator lamps to illuminate as a function of the property of the gas sensor detected by the controller.
A fan can be received in the housing in fluid communication with the inlet of the housing. The fan can be operated to urge the one or more gases into contact with the gas sensor, through the housing and through the outlet of the housing.
The leak detector can also include a power supply and an auto gain/biasing circuit received in the housing and connected to opposite sides of a heater element of the gas sensor. The auto gain/biasing circuit can operate to maintain the electrical power dissipated by the heater element constant regardless of variances in the resistance of the heater element.
We have also invented a portable leak detector having a housing with an inlet in fluid communication between an interior and an exterior of the housing and an outlet. A gas sensor having a property that changes in response to exposure of the gas sensor to one or more gases is disposed in fluid communication with the interior of the housing. The leak detector can include a plurality of first indicator lamps supported by the housing. A controller supported by the housing is connected to detect the property of the gas sensor. As a function of the detected property of the gas sensor, the controller causes a first group of the plurality of first indicator lamps to illuminate. In order to determine which group of first indicator lamps to illuminate, the controller detects the property of the gas sensor a plurality of times. Next, the controller determines from the plurality of detected properties a minimum property value, a maximum property value and a newest property value. Thereafter, the controller determines a property ratio. The property ratio is a ratio of the difference between the newest property value and the minimum property value over the difference between the maximum property value and the minimum property value. Thereafter, the controller illuminates the group of the first plurality of indicator lamps as a function of a product of the property ratio and a quantity of first indicator lamps.
The controller can also periodically detect the property of the gas sensor to obtain a new property value and can replace the oldest of the plurality of detected property values with the new property value. The controller can replace the minimum property value with the new property value if the new property value is less than the minimum property value and can replace the maximum property value with the new property value if the new property value is greater than the maximum property value. The controller can then determine another property ratio and can illuminate a second group of the plurality of first indicator lamps as a function of the other property ratio and the quantity of the plurality of the first indicator lamps. In the absence of a change between the new property ratio and the preceding property ratio, the quantity of the first group of the plurality of first indicator lamps and the quantity of the second group of the plurality of first indicator lamps are the same.